On Sun, 11 Feb 2024 22:15:16 -0800 (PST), Google Pandey
<gp481982@gmail.com> wrote:

On Monday 12 February 2024 at 11:34:33 UTC+5:30, Google Pandey wrote:

for relay switching circuit which transistor is perfer

if i'm getting 3.3v/0v input signal for base terminal

What's the coil voltage and current?

You could probably use a logic-level n-channel mosfet, something like
FDV301.

I'm designing a board that needs about 125 relays. Turns out that
modern nfets don't need flyback clamp diodes, which will save me some
room I need for routing traces.

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On Mon, 12 Feb 2024 07:05:27 -0800 (PST), Fred Bloggs <bloggs.fredbloggs.fred@gmail.com> wrote:

On Monday, February 12, 2024 at 1:04:33?AM UTC-5, Google Pandey wrote:

for relay switching circuit which transistor is perfer

Go back to the website for whatever it is you're using and search FAQs and Application section for 'relay drivers'. You're unlikely to comprehend anything more.

There are so many nasty people here.

--- SoupGate-Win32 v1.05
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On Mon, 12 Feb 2024 07:06:50 -0800 (PST), Fred Bloggs <bloggs.fredbloggs.fred@gmail.com> wrote:

On Monday, February 12, 2024 at 10:02:53?AM UTC-5, John Larkin wrote:

On Sun, 11 Feb 2024 22:15:16 -0800 (PST), Google Pandey
<gp48...@gmail.com> wrote:

On Monday 12 February 2024 at 11:34:33 UTC+5:30, Google Pandey wrote:

for relay switching circuit which transistor is perfer

if i'm getting 3.3v/0v input signal for base terminal

What's the coil voltage and current?

You could probably use a logic-level n-channel mosfet, something like
FDV301.

I'm designing a board that needs about 125 relays. Turns out that
modern nfets don't need flyback clamp diodes, which will save me some
room I need for routing traces.

Ridiculous response for the context.

What did you last use as a relay driver?

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

On Sun, 11 Feb 2024 22:04:29 -0800 (PST), Google Pandey
<gp481982@gmail.com> wrote:

for relay switching circuit which transistor is perfer

For more than one relay, take a look at ULN2003.

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

On 2/11/2024 11:26 PM, whit3rd wrote:

On Sunday, February 11, 2024 at 10:15:23 PM UTC-8, Google Pandey wrote:

On Monday 12 February 2024 at 11:34:33 UTC+5:30, Google Pandey wrote:

for relay switching circuit which transistor is perfer

if i'm getting 3.3v/0v input signal for base terminal

That's usually a CMOS output from an Arduino (or some such); the
relay, though, what does IT require? There's different answers for
the current to drive different relays.

Appliances (and trucks, and aircraft...) use 24V nominal.
Automobile (12V) relays might be 300 ohm windings, and require
a 12V power source (8 to 20V is probably close enough) which might
(or might not) be grounded to the same '0v' as your logic.

Take care to note the impact "ground bounce" can have on the
drive circuit -- and, if the *switched load* also shares that
ground!

And, of course, the fact that you may be disturbing the supply that (ultimately) powers your logic/drive circuit.

Many folks put a flyback diode as a snubber across the coil.
A better solution is a diode in series with a zener (rated
for the coil voltage) as this lets the relay operate
(mechanically) in a manner more similar to it's *design*
criteria.

If you want to drive more than one relay, there's ganged drivers
available (integrated circuits, cheap ones).

And, if driving multiple, you may want to *stagger* the drives
to avoid a large "disturbance" in your system.

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

On 2024-02-12, John Larkin wrote:

On Sun, 11 Feb 2024 22:15:16 -0800 (PST), Google Pandey
<gp481982@gmail.com> wrote:

On Monday 12 February 2024 at 11:34:33 UTC+5:30, Google Pandey wrote:

for relay switching circuit which transistor is perfer

if i'm getting 3.3v/0v input signal for base terminal

What's the coil voltage and current?

You could probably use a logic-level n-channel mosfet, something like
FDV301.

I'm designing a board that needs about 125 relays. Turns out that
modern nfets don't need flyback clamp diodes, which will save me some
room I need for routing traces.

They don't? I guess I'm not using "modern" NFETs then ... :(

Or are you just gonna rely on the body diode?

--
|_|O|_|
|_|_|O| Github: https://github.com/dpurgert
|O|O|O| PGP: DDAB 23FB 19FA 7D85 1CC1 E067 6D65 70E5 4CE7 2860

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

On Mon, 12 Feb 2024 09:25:39 -0800 (PST), Fred Bloggs <bloggs.fredbloggs.fred@gmail.com> wrote:

On Monday, February 12, 2024 at 10:36:52?AM UTC-5, John Larkin wrote:

On Mon, 12 Feb 2024 07:06:50 -0800 (PST), Fred Bloggs
<bloggs.fred...@gmail.com> wrote:

On Monday, February 12, 2024 at 10:02:53?AM UTC-5, John Larkin wrote:

On Sun, 11 Feb 2024 22:15:16 -0800 (PST), Google Pandey
<gp48...@gmail.com> wrote:

On Monday 12 February 2024 at 11:34:33 UTC+5:30, Google Pandey wrote:

for relay switching circuit which transistor is perfer

if i'm getting 3.3v/0v input signal for base terminal

What's the coil voltage and current?

You could probably use a logic-level n-channel mosfet, something like
FDV301.

I'm designing a board that needs about 125 relays. Turns out that
modern nfets don't need flyback clamp diodes, which will save me some
room I need for routing traces.

Ridiculous response for the context.

What did you last use as a relay driver?

I think I used one last summer to dig a splinter out of my thumb.

Was it a BGA?

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

Dan Purgert <dan@djph.net> wrote:

On 2024-02-12, John Larkin wrote:

On Sun, 11 Feb 2024 22:15:16 -0800 (PST), Google Pandey
<gp481982@gmail.com> wrote:

On Monday 12 February 2024 at 11:34:33 UTC+5:30, Google Pandey wrote:

for relay switching circuit which transistor is perfer

if i'm getting 3.3v/0v input signal for base terminal

What's the coil voltage and current?

You could probably use a logic-level n-channel mosfet, something like
FDV301.

I'm designing a board that needs about 125 relays. Turns out that
modern nfets don't need flyback clamp diodes, which will save me some
room I need for routing traces.

They don't? I guess I'm not using "modern" NFETs then ... :(

Or are you just gonna rely on the body diode?

Body diode doesn’t come into play. Some modern fets have published
avalanche energy ratings, so exceeding Vbvds can be permitted.

--
piglet

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

On Tue, 13 Feb 2024 11:11:57 -0000 (UTC), Dan Purgert <dan@djph.net>
wrote:

On 2024-02-12, John Larkin wrote:

On Sun, 11 Feb 2024 22:15:16 -0800 (PST), Google Pandey >><gp481982@gmail.com> wrote:

On Monday 12 February 2024 at 11:34:33 UTC+5:30, Google Pandey wrote:

for relay switching circuit which transistor is perfer

if i'm getting 3.3v/0v input signal for base terminal

What's the coil voltage and current?

You could probably use a logic-level n-channel mosfet, something like
FDV301.

I'm designing a board that needs about 125 relays. Turns out that
modern nfets don't need flyback clamp diodes, which will save me some
room I need for routing traces.

They don't? I guess I'm not using "modern" NFETs then ... :(

Or are you just gonna rely on the body diode?

Lots of mosfets have explicit avalanche ratings. Just out of
curiosity, I tested a few that didn't, including a 2N7002 and an
FDV301. Both avalanched nicely at around 20% over rated voltage, which
sounds deliberate to me. Somebody here said that all modern mosfets
have controlled avalanche.

I might chicken out and invest 3 cents in an explicitly
self-protecting part, but it doesn't seem necessary.

My thinking is that I can put one SOT-23 fet under each relay, on the
back side of the board, driven by one FPGA ball. All 125 fet drive
signals could be routed on one PCB layer.

https://www.dropbox.com/scl/fi/34vn0wrhy57jzfzl2mse0/P948_trial.jpg?rlkey=r6vqi22zxqmjbmdt0s30bs0s0&raw=1

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

On Tue, 13 Feb 2024 08:21:23 -0800 (PST), Lasse Langwadt Christensen <langwadt@fonz.dk> wrote:

tirsdag den 13. februar 2024 kl. 16.39.08 UTC+1 skrev John Larkin:

On Tue, 13 Feb 2024 11:11:57 -0000 (UTC), Dan Purgert <d...@djph.net>
wrote:

On 2024-02-12, John Larkin wrote:

On Sun, 11 Feb 2024 22:15:16 -0800 (PST), Google Pandey
<gp48...@gmail.com> wrote:

On Monday 12 February 2024 at 11:34:33 UTC+5:30, Google Pandey wrote:

for relay switching circuit which transistor is perfer

if i'm getting 3.3v/0v input signal for base terminal

What's the coil voltage and current?

You could probably use a logic-level n-channel mosfet, something like
FDV301.

I'm designing a board that needs about 125 relays. Turns out that
modern nfets don't need flyback clamp diodes, which will save me some
room I need for routing traces.

They don't? I guess I'm not using "modern" NFETs then ... :(

Or are you just gonna rely on the body diode?

Lots of mosfets have explicit avalanche ratings. Just out of
curiosity, I tested a few that didn't, including a 2N7002 and an
FDV301. Both avalanched nicely at around 20% over rated voltage, which
sounds deliberate to me. Somebody here said that all modern mosfets
have controlled avalanche.

mybe, https://www.infineon.com/dgdl/Infineon-ApplicationNote_Some_key_facts_about_avalanche-ApplicationNotes-v01_01-EN.pdf?fileId=5546d462584d1d4a0158ba0210977cde

Even when fets are specified for avalanche energy, there is seldom a
hint of what the avalanche voltage might be.

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

On Tue, 13 Feb 2024 12:54:23 -0800 (PST), Fred Bloggs <bloggs.fredbloggs.fred@gmail.com> wrote:

On Monday, February 12, 2024 at 10:34:42?AM UTC-5, John Larkin wrote:

On Mon, 12 Feb 2024 07:05:27 -0800 (PST), Fred Bloggs
<bloggs.fred...@gmail.com> wrote:

On Monday, February 12, 2024 at 1:04:33?AM UTC-5, Google Pandey wrote:

for relay switching circuit which transistor is perfer

Go back to the website for whatever it is you're using and search FAQs and Application section for 'relay drivers'. You're unlikely to comprehend anything more.

There are so many nasty people here.

It is the only reasonable response in the whole thread. OP is hobbyist working with a hobbyist part/ project. He is best served by the tutorials on the hobby project site. All those sites can be searched. I told him to search for 'relay drivers'. It's

ridiculous to talk about avalanche energy, SOAs, various types of relays, or even just current. The hobby site will teach him how to go from low voltage logic output to a relay input.

I don't mind helping beginners. Their questions sometimes evoke
interesting issues.

My pcb designer thinks he can route out 134 available balls of our
FPGA, and I think I can drive all those relays with just one sot23 fet
under each relay.

We'll selective-solder the thru-hole relay pins and the solder nozzle
will just barely not desolder the fet.

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